In most cases, a wireless communication terminal, such as a smartphone, or a tablet terminal, includes an interface for various wireless communication. The interfaces for wireless communication that are included in the wireless communication terminal include, for example, interfaces such as local area network (LAN), 3rd Generation (3G: a third mobile communication system), and Long Term Evolution (LTE). For example, in the case of the wireless LAN, the wireless communication terminal performs coupling to an access point (AP) in the vicinity, and thus can perform coupling to the Internet or a local network. The wireless communication terminal is simply referred to as a terminal.”
Because a reach range of an electromagnetic wave of the AP is several tens of meters, in a case where coverage in a broader range is desired, in most cases, APs are installed at distances of 20 to 30 meters. In a place where a lot of people gather locally such as a sports stadium or a hotel lobby, although the APs are installed at given distances, coupling by terminals is concentrated on a specific AP, and communication speed decreases.
This is due to specifications for terminals in the wireless LAN, which state that a coupling to an AP that has the highest received signal strength indicator (RSSI) is made. The received signal strength indicator is also called a received electromagnetic wave strength. For example, in a case where electromagnetic output strengths of all the APs within the network are the same, the shorter the distance to the terminal is, the stronger the received electromagnetic wave strength of the output electromagnetic wave from the AP becomes. For this reason, a terminal performs coupling to the AP that is positioned the closest to the terminal. Therefore, in a case where a lot of people gather locally, the coupling by the terminals is concentrated on the AP that is positioned the closest to the place where they gather. As a result, an electromagnetic wave occupancy rate per one terminal decreases, and communication speed decreases.
As a method of suppressing the concentration of accesses by terminals to a specific AP, for example, a method is known in which a terminal is caused to acquire a congestion situation of an AP in the vicinity and to perform coupling to an AP that is not congested. Furthermore, in addition, for example, a method is known in which a wireless LAN controller that controls the AP monitors the congestion situation of each AP, coupling by multiple terminals to the AP that is in congestion is released, and thus a load on the AP that is in congestion is alleviated. Moreover, the expression “An AP is in congestion” means that the electromagnetic wave occupancy rate per one terminal that performs coupling to the AP is below a threshold at which the communication speed is maintained to such an extent that a user of the terminal does not feel discomfort. That is, the expression “An AP is in congestion” means that the number of the terminals that perform coupling to the AP or the electromagnetic wave occupancy rate of the AP is a threshold or above.
As examples of the related art, Japanese Laid-open Patent Application Publication No. 2004-140614, Japanese Laid-open Patent Application Publication No. 2014-192899, and Japanese Laid-open Patent Application Publication No. 2009-111768 are known.